Field of the Invention
The present invention relates to an electron beam alignment method and electron microscope.
Description of Related Art
In transmission electron microscopes (TEMs), a beam alignment is generally performed using a voltage axis alignment or current axis alignment technique (see, for example, JP-A-60-167248).
In recent years, transmission electron microscopes have tended to have higher resolution. With this trend, it is said that during high-resolution imaging, it is more important to align the direction of incidence of the electron beam with a coma-free axis than implementing any of the above-mentioned alignment techniques. On the coma-free axis, on-axis comatic aberration that is one of parasitic aberrations in an objective lens is null.
In this way, in a transmission electron microscope, it is important to align the incident direction of the electron beam with a coma-free axis. Accordingly, there is a need for a technique whereby a beam alignment with a coma-free axis is performed easily.